Method and an apparatus for the production of shaped articles

Abstract

Plastics-forming materials are shaped in a mold tool sealed by an associated closing unit. Lifting elements the stroke of which can be limited and controlled are associated with the mold tool. Shaping is accomplished by filling the mold cavity with reaction mixture while the mold tool halves are not completely sealed, sealing the filled mold and keeping the mold sealed until the article is completely cured. This method and apparatus are particularly useful in the production of dimensionally accurate geometrically complicated shaped articles.

What is claimed is: 
     
       1. A method for producing shaped articles in which: (a) a mold tool is placed in a first position in which the shaping surfaces of the mold tool are brought together but are not completely closed to a distance of up to 5 mm from the closed position,   (b) introducing a reaction mixture into the molded tool,   (c) completely closing the mold tool when the mold is filled with reaction mixture,   (d) building up the pressure in the closed mold tool,   (e) curing the article thus-molded,   (f) opening the mold tool and,   (g) removing the molded article from the mold tool.   
     
     
       2. The method of claim 1 in which the shaping surfaces are brought towards one another to a distance of from 0.01 mm to 1 mm from the closed position in (a). 
     
     
       3. The method of claim 1 in which the closing in (c) is carried out in several stages. 
     
     
       4. The method of claim 1 in which final closing of the mold is prevented during (b) by a counterforce exceeding the closing force which counterforce is reduced upon completion of step (b). 
     
     
       5. An apparatus for producing shaped articles from a reactive mixture comprising: (a) a mold tool having two halves,   (b) lifting elements associated with mold tool (a) the stroke of which can be limited and controlled, and   (c) a closing unit having two base plates each of which is associated with one or the other mold tool half in which lifting elements (b) act against the closing force of closing unit (c) during introduction of the reactive mixture.   
     
     
       6. The apparatus of claim 5 in which the lifting elements (b) are hydraulic units with piston and cylinder. 
     
     
       7. The apparatus of claim 5 in which the lifting elements (b) are hydraulic pressure cushions. 
     
     
       8. The apparatus of claim 5 in which the lifting elements (b) are arranged on the closing unit (c). 
     
     
       9. The apparatus of claim 5 in which the lifting elements (b) are arranged on one of the base plates of closing unit (c) and adjustable supporting elements (d) are arranged on the other base plate of closing unit (c). 
     
     
       10. The apparatus of claim 5 which further comprises (e) a force generating system for lifting elements (b), (f) a force generating system for closing unit (c) and (g) a mixing device with a programmer for material to be fed into the mold tool (a). 
     
     
       11. The apparatus of claim 10 which further comprises (h) a control device associated with the programmer of mixing device (g). 
     
     
       12. The apparatus of claim 11 in which the force generating systems (e) and (f) are connected to the programmer of mixing device (g).